[R] How to take difference of sets when there is an empty subset involved

Neha Aggarwal aggarwalneha2000 at gmail.com
Sun Mar 18 16:00:11 CET 2018

Hello,

Problem I am facing is as follows:

Set A is made of 2 sets x and y
x<-{"P1", "P2", "P3", "P4"}
y<-{}
A<-set(x,y)
#A={{}, {"P1", "P2", "P3", "P4"}}

i need to use A in a recursive loop where i need to take set difference of
A and it 's elements.
Example:
for (i in A){
print(i)
A<-set_symdiff(i,A)    ###Imp line i need help on
print(A)
}

the program is unable to recognise the empty set in the set A. I tried
various  methods in Imp line above:
> A-i
#Output : {{}, {"P1", "P2", "P3", "P4"}}
> set_symdiff(i,A)
Output: {{}, {"P1", "P2", "P3", "P4"}}
> set_symdiff(A,i)
Output: {{}, {"P1", "P2", "P3", "P4"}}

i also tried with set_complement() .But it does not subtract the empty
subset from the bigger set. It seems it doesn't recognise it.
What else can I try ? any pointers/ packages will be great help.

.
Thanks in advance,
Neha

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